It is known to repair spinal injuries and correct spinal problems, specifically cervical related injuries, using a plate. Plates are typically affixed to one or more vertebral bodies using bone screws which thread through openings in the plate and into the vertebral bodies. Some bone screw and plate assemblies, unfortunately, require that the screw be inserted at a fixed insertion angle that is perpendicular to the plate. These plates are difficult to use due to the lack of variability in insertion angle. In poor quality bone these plates are prone to subsidence, decreased rate of fusion, and subsequent failure.
Other current systems do not provide a rigid attachment in the vertebral body. The screw head is able to toggle within the plate. The screws are therefore able to move within the vertebral body causing shear stress to the trabecular bone, which is weakest in shear. Bone screws are typically attached at a single point or two points of fixation. Thus, so long as the patient load is less than the shear frictional force, the construct of bone screw and plate is stable. However, because the screws have only one or two points of fixation, if the patient load at that location exceeds the shear frictional force, then the construct may be unstable and could potentially fail. Typically, in poor quality bone, minimal force is needed to pull out a plate with single points of fixation.
Accordingly, what is needed in the art is a spine repair system and assembly that is easy to attach and capable of locking the bone screw and plate, provides for a variable angle of attachment only in certain angles and has increased rigidity within the vertebral body.